First thought would be a 595 shift register, you get a heck of a lot more than 10 outputs with just 3 inputs. 8 outputs per chip, daisychain the chips without using any more pins from the arduino. Very versatile.http://arduino.cc/en/Tutorial/ShiftOut

But if you're really looking for just one pin maybe you need to find something that works with serial communication... I wouldn't know much about that.

If I understand your question correctly you want to send PWM to one of 10 wires using as few Arduino outputs as possible.

Using 3 pins you can use the ShiftPWM library (I think that's what it is called) that simulates PWM using 595 shift registers. I have had up to 32 PWM outputs driving leds simultaneously using an Uno.

Using 2 pins you could clocking a CD4017 IC with one pin (each clock pulse turns on the next output from the chip), feeding that into a transistor to switch the PWM line to one of 10 outputs. Look for the datasheet to see how it works.